Method of vulcanizing rubber and resulting products



Patented Nov. 5, 1929 HENRY E. MORSE, E DAMVEES, MASSACHUSETTS, nssienon; BY MESNE ASSlIGNMENTS, To ALBERT o. BURRAGE, m. OF IPSWICH, ASSACHUSETTS METHOD OF VULCANIZI IING RUBBER AND. RESULTING PRODUCTS No Drawing. Application filed June 4,

This invention relates to the art of treating rubber'or rubber compounds, and has for an object the provision of an improved procedure for the vulcanization of the same in the presence of an accelerator and of compounds or compositions with which to effect the purpose of the invention.

In the art of rubber manufacture, it has long been known that the vulcanizing process 1 0 may be accelerated by the addition ofvarious accelerate the reaction in the customary vul-' canizing treatment.- Other accelerator compounds, frequently termed ultra accelerators or semi-ultra accelerators, initiate the vulcanizing reaction sometimes prematurely, either in the cold only or during the mixing operation, resulting in scorching which hinders or entirely prohibits the further use of the rubber or rubber compound. Consequently, such compounds ordinaril have not been usedin the manufacture of mi ber prod.- ucts,even though they would greatly reduce the time required for vulcanization and may positions. e v I By the present invention it is found that the accelerating action of accelerator compounds generally in rubber compositions, may be inhibited (at ordinary and slightly a further substitution may be introduced into elevated temperatures and during the mixing and milling operations) or retarded by the.

addition of organic compounds of a'certain type hereinafter defined, and that thereafter the vulcanizing reaction,eifectively accelappreciable vulcan-,

be otherwise suitable for use in rubber comerated by'the'accelerator,--may be caused to Y 1929. Serial no. 368,433.

proceed at will by subjecting the rubber composition to be vulcanized to vulcanizing'comditions.

It is thought that the accelerator and the inhibitorreact or combine to form a reaction product or compound which does not promote the vulcanizing reaction of the vulcanizable composition (under the preliminary conditions such as mixing and milling) but which, under the Vulcanizing conditions such asincreased temperature, dissociates and liberates the accelerator which then acts in its accelcrating capacity, and the inhibitor may remain inert or may itself act as an accelerator.

Inother words, the critical temperature of i the accelerator, with respect to its initiating prematurely the vulcanizing reaction in the rubber, is apparently raised, to a point'above the temperatures of milling or compounding and within the range of the vulcanizing treatment.

The compounds manifesting such inhibiting action upon premature initiation of vulcanization by accelerators (and more especially the ultra accelerators and those sometimes referred "to as semi-ultra accelerators among which maybe mentioned the thiazoles, represented by mercapto benzo thiazole, certain disulfides such as tetra methyl thiuram disulfide, certain monosulfides such as tetra methyl thiuram monosulfide, etc., and their derivatives) are found to typically include the nitroso-amines which may be represented by the empirical formulai in which R and R represents alkyl or aryl radicals (or nuclei) which may be alike or unlike and in turn may contain or be associated with one or more substituents "Thus, in diaryl substituted nitroso-amines,

both of the aryl radicalsor nuclei lit and R, which is typically inonovalent andpreferably an alkyl hydrocarbon, such as the methyl group in diorthotolyl nitr'oso-amine.

In a representative example of the invenoccurred.

tion, rubber and the usual vulcanizing and filler materials, together with the desired amounts of the accelerator compound and inhibiting compound, maybe compounded and mixed in the usual manner as by milling (without premature vulcanization or scorching and subsequently molded and vulcanize to the required degree of cure, by heating to the usual range of vulcanization temperatures. The rate of vulcanization and degree of cure obtained may be accurately controlled by the time and temperature of vulcanization, to provide a final cure equal toor better than that obtained 'without the use of the preliminary inhibiting compound or prehibitor.

In a preliminary scorching test, for example, in which the compounds were subjected to especially high temperatures during the mixing and milling operations until scorching was effected, a rubber composition containing;

100 parts rubber (smoked sheet) 3 parts sulfur 5 parts ZnO part mercapto benzothiazole to which .43 part dibeta naphthyl nitrosoamine was added, was thoroughly milled and mixed on the mixing rolls; the mix was then removedand again milled on rolls, purposely heated by steam so as to maintain a temperature in the stock of approximately 95 to 100 C., for 110 minutes before scorching A correspondin stock without the addition of dibeta nap thyl nitroso-amine, upon being milled and mixed, and again milled under like conditions of temperature, scorched in 65 minutes.

A similar test carried out upon a rubber compound of the formula:

produced scorching in about 72 minutes. Under like conditions the same compound, without the dibeta naphthyl nitroso-amine, was scorched in twenty minutes.

A third compound, having the formula:

100 parts rubber (smoked sheet) 3 parts sulfur 5 parts ZnO .15 parti tetra methyl thiuram monosul .75 part dibeta naphthyl nitroso-amine was treated in the same way as the preceding compounds and scorching took place in 118 minutes, while the same compound, without d beta naphthyl nitroso-amine, was

scorched in about 65 minutes, under the same conditions.

This test, developed for the purpose, serves TABLE I Stock Rubber 100 Sulfur 1 3 Zinc oxide 5 Tetramethyl thiuram disulfide 0.15

Minutes before scorching Stock without prehibitor 44 With addition of 0.75part of Diphenyl nitroso-amine 110 Dialpha naphthylnitroso-amine 62 Phenyl beta naphthylnitrosoamine 93 Phenyl alhpa naphthylnitrosoamine 93 Diorthotolyl nitroso-amine Phenyl orthotolyl nitroso-amine 102 Phenyl paratolyl n'itroso-amine 102 Benzyl phenyl nitroso-amine 52 Methyl phenyl nitroso-amine 57 Diethyl nitroso-amine 55 Piperidine nitroso-amine 55 Carbazol nitroso-amine 46 In a typical application of the invention to the usual vulcanizing procedure, rubber compounds were prepared as follows:

100 parts rubber 40.5 parts'carbdn black 5.0 parts ZnO 3.0 parts sulfur, 5.0 parts mineral rubber 3.0 parts stearic acid .8 part mercapto benzo thiazole IV Table III Same as Formula I with addition of .50 A B C part diphenyl nitroso-amine. D

These were mixed by milling in the usual Smoked sheets 100 100 100 I00 manner, care being taken, espec ally with the 40 40 40 40 compound of Formula I, to prevent prelimi- )2 g g g nary vulcanization or scorching. The mixed g g 3 compounds were then laid in thin sheets in a Mercaptofld 0.8 0.8 0.8 0.8 vulcanizing mold and vulcanized at 20 pounds gf 'jg ffff ffffff f l o 0. 75 0 p 0 steam pressure. Samples of each compound Benzyl phqnyl 0 0 0 Carbazol nitroso-amiue 0 0 0 0. .5 were vulcanized, for periods of 30, and 1 l minutes, respectively. One portion of each sample was then sub ected to a tensile Cure Firm Final strength test the results being given in the tensile elongaf Stock I, d 300% 500% lbs. per tion in QIlOWlIlg table 0 Min D1223: sq. in. per cent TABLE II 80 20 740 I 2010 3335 660 60 20 737 2110 3535 665 60 20 821 2200 3720 670 Cure at twenty pounds steam pressure 60 20 843 2250 3060 (S70 75 20 880 2390 3010 065 30 Minutes 75 20 985 2600 4260 705 75 20 850 2280 3700 I 650 I 20 930 2460 3890 660 2 s 88 2s ensi e e onga- 9 2 1 8 7 6 300% 500% lbs. per tion in 90 20 960 2580 3050 050 sq. in. per cent A 735 1005 3400 685 Table IV A 380 1140 2120 675 A 583 1675 2930 680 A B C D A 3 3100 665 Smoked sheets 100 100 100 40 40 40 40 5 5 5 5 45 Minutes 3 g g g 3 s a a v 0.8 0.8 0.8 0.8 gim i {final Ph 1 b t hm 1 5e 0 0. 75 0 0 as e e on 8- en e a na y nitroso- 300% 50.0% lbs.per tion in ami i ie Hf 0 O 0.75 0

sq.1n. percent naphthyl nitrosoamine 0 0 0. 0.15

II A 112 2000 3420 680 III A 948 2440 4125 675 Cure Final Final r I Stdck 800% 500% 521 383%; IV A 010 2500 4150 615 M n 5333f sq. in. percent 00 20 590 i965 3590 710 60 Minutes 60 20 830 2240' 4000 700 60 20 I 762 2100 3700 700 i I" g inal 00 l 20 667 1900 3200 655 1 1 75 '20 850 2200 3890 700 500% 75 20 867 2360 3850 050 qpercent 75 20 900 2365 3840 005 75 20 840 2320 3760 655 I A 1105 2830' 00 20 040 230 3 0 1 90 20 985 0 7 II 2660 20 iii A 1135 2880 4175 835 4000 655 IV A 1120 2080 4280 625 Table V Similar vulcanizing experiments were car- A B o D ried out with compositions containing other nitro'so-amines, including both like and un gmoked m I 1 1% 1 1 like substituent groups, and hydrocarbon fififi fi 5 5 5 5 radicals of both the aliphatic and aromatic g3 9 g g g 2 series, as indicated in the above list in coneari1 i&%iI I g g g 3 u e n B nection with the scorching test. ,;3 %f, g, m13;? g .15 g 75 g 1 [I 116111 row-ammo..- The experimental results are presented in gg phenymtmwammmm 0 0 0 M5 the following tables:

Cum Final Final 0000 Pounds 000% 000% are 2222a; Min pressure sq. in. per cent Table ,VI

A B C D Smoked sheets 100 100 100 100 Carbon black 40 40 40 Mineral rubber 5 5 5 5 Zinc oxide 5 5 5 5 Sulfur 3 3 3 3 Stearic acid 3 3 3 3 Mercapto benzo thiazole 0.8 0.8 0.8 0.8 Dialpha naphthyl nitroso-amine. 0 0. 75 0 0 Phenyl tolyl nitroso-amine- 0 0 0.75 0 Ditolyl nitroso-amine 0 0 0 0. 75

Cum Final Final- 0000 Pounds 000% 000% are as:

Mm pressure sq. m. per cent 0 v i From the data thus obtained it is to be obsition to which such addition has not been made.' 7

It is therefore shown that by means of this invention not only may extremel active accelerators, (which have been hitherto unavailable for use in the rubber industry on account of their very high activity) be safely employed in rubber compounds and mixed and milled without initiating premature vulcanization, but the vulcanized rubber prodnot is initially as good or better than rubber similarly compounded and vulcanized but bazol nitroso-amine which may be spoken of as nitroso N-carbazol.

N.NO

Carbazol nitroso-amine or nitroso N-carbazol, however, is not strictly in the same category with the other compounds tested and in fact shows but little retarding effect in the scorching test. The-piperidine nitroso-amine likewise does not manifest pronounced retarding effects. The results are given, how ever, because they are related to the other nitroso-amine compounds. Their failure to be more effective 1n these respects may be attributed to the valence linkage between the R and R groups of the nitroso-amine; which will be apparent from the formula of the former compound, as above given.

While the above disclosure relates to a preferred procedure, according to the invention, and to specific reagents employed in specific 4 proportions, it is to be understood that variations may be made in both the mode of carrying out the invention and in the nature and amount of the several rea ents used, according to the. particular conditions of practice and the characteristics desired in the resulting product, as will be clear to those skilled in the art of treating rubber.

This application is a continuation in art of my application, Serial No. 323,556, led December 3, 1928, and is designated as Case III9 of a group of continuation applications filed on even date herewith.

I claim: v

1. Method of vulcanizing rubber or rubber compositions with a vulcanizin agentand an organic accelerator characterlzed by controlling .the action of the accelerator with a diaryl substituted nitroso-amine characterized by containing a methyl radical in both of the ar 1 nuclei.

2. Met 0d of vulcanizing rubber or rubber compositions with a vulcanizin a cut and an organic accelerator characterlze by controlling the action of the accelerator-with a ditolyl nitroso-amine.

3, ,Method of vulcanizing rubber or rubber compositions with a vulcanizing agent and an orgamc accelerator characterized by controlcompositions with a vulcanizing agent and a sulphur-containing organic accelerator characterized by controlling the action of the .accelerator with diorthotolyl nitroso-amine.

7. Method of vulcanizing'rubber or rubber compositions withfia vulcanizing agent and an accelerator COIltilll'llIl a thiazole nucleus characterized by controlling the action of the accelerator with a diaryl'substituted nitrosoamine characterized by containing a methyl radical in both of the aryl nuclei.

8. Method of vulcanizing rubber or rubber compositions with a vulcanizing agent and an accelerator containing a thiazole nucleus characterizedby controlling the action of the accelerator with a ditolyl nitroso-amine.

9. Methodof vulcanizing rubber or rubber compositions with a vulcanizing agent and an accelerator containing a thiazole nucleus characterized by controlling the action of the accelerator with diorthotolyl nitrosoamine.

10. Method of vulcanizing rubber or rubber compositions with a vulcanizing agent and 16. An accelerator composition comprising a sulphur-containing organic accelerator and a diaryl substituted nitroso-amine characterized by containing a methyl radical in both of the aryl nuclei.

17 An accelerator composition comprising a sulphur-containing organic accelerator and a ditolyl nitroso-amine.

18. An accelerator composition comprising a sulphur-containing organic accelerator and diorthotolyl nitroso-amine.

19. An accelerator composition comprising an accelerator containing a thiazole nucleus and a diaryl substituted nitroso-amine characterized by containing a methyl radical in both of the aryl nuclei.

20. An accelerator composition comprising an accelerator containing a thiazole nucleus and a ditolyl nitroso-amine.

21. An accelerator composition comprising an accelerator containing a thiazole nucleus and diorthotolyl nitroso-amine.

22. An accelerator composition comprising mercapto benzothiazole and a diaryl substituted nitroso-amine characterized by containirlig a methyl radical in both of the aryl nu- 0 e1.

23. An accelerator composition comprising mercapto benzo thiazole and a ditolyl nitrosoamine.

24. An accelerator composition comprising mercapto benzo thiazole and a diorthotolyl nitroso-amine.

Signed by me at Boston, Massachusetts, this 1st day of June, 1929. I HENRY B. MORSE.

mercapto benzo thiazole characterized by controlling the action of the accelerator with a diaryl substituted nitroso-amine characterized by containing a methyl radical in both of the aryl nuclei.

11. Method of vulcanizing rubber or rub ber compositions with a vulcanizing a ent and merca to benzo thiazole characterized by controllmg the action of the accelerator with a ditolyl nitroso-amine.

12. Method of vulcanizing rubber or rubber compositions with a vulcanizing agent and mercapto benzo thiazole characterized by controlling the action of the accelerator with diorthotolyl nitroso-amine.

13. An accelerator composition comprising an organic accelerator and a diaryl substituted nitroso-amine characterized by containing a methyl radical in both of the aryl nuclei.

14. An accelerator composition comprising an organic accelerator and a ditolyl nitrosoamine.

15. An accelerator composition com rising an organicaccelerator and diorthoto yl nitroso-amine. 

